Prior to about 1930 the principal cause of corrosion of underground metallic structures was stray current from d-c operated trolley cars. The extension of trolley lines into interurban service came with similar extension of underground telephone cables so that these cables all were under the influence of stray current. The same is largely true of other underground structures. Because stray current effects greatly overshadowed other causes of corrosion they were considered to be the sole cause.
The control of stray current and its effects were shrouded in mystery by some engineers who sold their services largely on the basis that they only could devise proper methods of control. This practice became so widespread that a committee was formed to investigate stray current effects, explain the phenomenon clearly and simply, and recommend methods of control. This committee was headed by the United States Bureau of Standards and had representatives of owners...
